A New Technique to Study Seals Habitats in Alaska

One harbor seal resting on the glacier ice (Source: Jamie Womble/NPS)
One harbor seal resting on the glacier ice (Source: Jamie Womble/NPS)

There are numerous harbor seals (Phoca vitulina) living in tidewater glacier fjords in Alaska. Harbor seals are covered with short, stiff, bristle-like hair. They reach five to six feet (1.7-1.9 m) in length and weigh up to 300 pounds (140 kg). Tidewater glaciers calve icebergs into the marine environment, which then serve as pupping and molting habitat for harbor seals in Alaska. Although tidewater glaciers are naturally dynamic, advancing and retreating in response to local climatic and fjord conditions, most of the ice sheets that feed tidewater glaciers in Alaska are thinning. As a result, many of the tidewater glaciers are retreating. Scientists are studying the glacier ice and distribution of harbor seals to understand how future changes in tidewater glaciers may impact the harbor seals.  Jamie Womble, a marine ecologist based in Alaska, is one of them.

Harbor seals on the glacier ice. (Source: Jammie Womble/NPS)
Harbor seals on the glacier ice (Source: Jamie Womble/NPS).

As Womble put in her recently published paper in PLOS One, “The availability and spatial distribution of glacier ice in the fjords is likely a key environmental variable that influences the abundance and distribution of selected marine mammals; however, the amount of ice and the fine-scale characteristics of ice in fjords have not been systematically quantified. Given the predicted changes in glacier habitat, there is a need for the development of methods that could be broadly applied to quantify changes in available ice habitat in tidewater glacier fjords.”

Map of Wombls's study area(source: Robert W. McNabb).
Map of Wombles’s study area (Source: Robert W. McNabb).

To conduct her research, Womble has used a variety of analytical tools including geospatial modeling (GIS), multivariate statistics, and animal movement models to integrate behavioral and diet data with remotely-sensed oceanographic data. Most recently, she has worked with object-based image analysis (OBIA).

“OBIA is a powerful image classification tool. Many people studying forests and urban areas use it,” Anupma Prakash, a colleague of Womble and professor of geophysics at the University of Alaska, told GlacierHub. “In our case, we could not use the satellite images because the satellite images did not have the details we required. We flew our aircraft quite low so we saw a lot of detail and could identify individual icebergs.”

OBIA offers an enhanced ability to quantify the morphological properties of habitat. Satellite imagery, on the other hand, is not a viable method in Alaska as there are few cloud free days.

 

“We wanted to classify our images into water, iceberg, and brash-ice (small pieces of ice and water all smushed together),” Prakash added. “The color and smoothness of water helped us isolate it. For icebergs the color, shape, and angular nature helped us isolate it, and the rest was bash-ice.” So it is now feasible to quantify fine-scale features of habitats in order to understand the relationships between wildlife and the habitats they use.

Harbor seals on the ice (source: Jamie Womble/NPS).
Harbor seals on the ice (Source: Jamie Womble/NPS).

Thanks to the work of scientists like Womble and Prakash, OBIA can now be applied to quantify changes in available ice habitat in tidewater glacier fjords. The method can also introduced in other geographic areas, according to professor Prakash.  Now that there is a more advanced method to study the harbor seals in Alaska, the hope is that other researchers will use the OBIA method to make further discoveries about key ocean habitats.

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Roundup: Everest, Subglacial Microbiomes, and Tidewater Glaciers

Roundup: Everest, Anaerobes & Fjords

 

China Tries to Conquer Everest

From Bloomberg: “Earlier this year, China opened a new paved road that winds 14,000 feet up the slope [of Mount Everest] and stops at the base camp parking lot. Plans are in the works to build an international mountaineering center, complete with hotels, restaurants, training facilities, and search-and-rescue services. There will even be a museum… What’s bad for Nepal will likely turn out to be a boon for tourists. Instead of fencing off Everest as a pristine wilderness, much as the U.S. has done with its national parks, China is approaching the Himalayas as the Europeans have the Alps… And if China sticks to it, it may well become the world’s new gateway to the Himalayas.”

Interested in learning more? Read the latest news here.

China opened a new paved road to Mount Everest (source: Mudanjiang Regional Forum).
China’s new paved road to Mount Everest (Source: Mudanjiang Regional Forum).

 

Implications for the Subglacial Microbiome

From Microbial Ecology: “Glaciers have recently been recognized as ecosystems comprised of several distinct habitats: a sunlit and oxygenated glacial surface, glacial ice, and a dark, mostly anoxic [absence of oxygen] glacial bed. Surface meltwaters annually flood the subglacial sediments by means of drainage channels. Glacial surfaces host aquatic microhabitats called cryoconite holes, regarded as ‘hot spots’ of microbial abundance and activity, largely contributing to the meltwaters’ bacterial diversity. This study presents an investigation of cryoconite hole anaerobes [organisms that live without air] and discusses their possible impact on subglacial microbial communities.”

Learn more about this study here.

Photomicrograph of Gram-stained enrichment culture, showing several cell morphotypes (source: Implications for the Subglacial Microbiome).
Photomicrograph of Gram-stained enrichment culture, showing several cell morphotypes (Source: Microbial Ecology).

 

Analysis of Icebergs in a Tidewater Glacier Fjord

From PLOS ONE: “Tidewater glaciers are glaciers that terminate in and calve icebergs into the ocean. In addition to the influence that tidewater glaciers have on physical and chemical oceanography, floating icebergs serve as habitat for marine animals such as harbor seals. The availability and spatial distribution of glacier ice in the fjords is likely a key environmental variable that influences the abundance and distribution of selected marine mammals… Given the predicted changes in glacier habitat, there is a need for the development of methods that could be broadly applied to quantify changes in available ice habitat in tidewater glacier fjords. We present a case study to describe a novel method that uses object-based image analysis (OBIA) to classify floating glacier ice in a tidewater glacier fjord from high-resolution aerial digital imagery.”

Read more about this study here.

Map of Johns Hopkins Inlet study area (source: Quantification and Analysis of Icebergs in a Tidewater Glacier Fjord Using an Object-Based Approach).
Map of Johns Hopkins Inlet study area (Source: PLOS ONE).
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